A self-defined intermediate product captured from the evolution process from a six-pod to an octahedral PbS sub-micrometer particle

Abstract

A sub-micrometer PbS particle with hierarchical structure, in which each octahedron was composed of six self-defined sub-octahedrons, was captured as the intermediate product in an evolution process from a six-pod to an octahedral-shaped PbS crystal. Moreover, the six sub-octahedrons of each octahedron presented almost intact octahedral morphology as well. Cl⁻ was found to be a good structure-directing agent that changed the growth habit of the PbS crystals and helped in the formation of a hierarchical octahedron (HO). Compared with other reported products with similar octahedral growth habit, the formation of a HO required a special equilibrium between a thermodynamic and kinetic growth regime, which resulted in the ratio of 3.46 of the average growth rate along the <100> direction to that along the <111> direction. The local supersaturation degree (LSD) around each individual nucleus was proposed to represent the real driving force that determined the different growth mechanisms. This study may be helpful for the design and synthesis of desired structures that are thermodynamically unstable.